1. Field of the Invention
The disclosures herein generally relate to a liquid-ejection head and an image forming apparatus.
2. Description of the Related Art
There is known in the related art a liquid-ejection head for use in image forming apparatuses such as printers, facsimile machines, etc. Such a liquid-ejection head is provided with piezoelectric elements, a diaphragm, and a pressure liquid chamber such that the piezoelectric element applies pressure to the pressure liquid chamber via the diaphragm to cause the liquid-ejection head to eject liquid droplets.
In the liquid-ejection head having such a configuration, the diaphragm and the piezoelectric element forming the pressure liquid chamber need to be located and bonded with high precision. Bonding adhesive is generally used for bonding the diaphragm and the piezoelectric elements; however, this type of adhesive does not have fast curability. Hence, in general, the diaphragm and the piezoelectric elements are temporarily adhered with fast-curing adhesive. As a related-art technology for preventing bonding adhesive and the fast-curing adhesive from mixing, a level difference is formed in one of the diaphragm and the piezoelectric elements at positions (e.g., end parts) to which bonding adhesive is not applied, and the fast-curing adhesive is applied to the level differentiated positions so as to temporarily fix the diaphragm and the piezoelectric elements.
Japanese Laid-open Patent Publication No. 2003-276207 (hereinafter referred to as “Patent Document 1”), for example, discloses an example of such technology for preventing the bonding adhesive and the fast-curing adhesive from mixing. In this technology, for the purpose of obtaining initial adhesive strength at the temporary fixing, a recess part is formed in an area of the diaphragm that faces an area of the piezoelectric elements to which the bonding adhesive is not applied, and the diaphragm and the piezoelectric elements are fixed by applying the fast-curing adhesive to the recess part.
However, in the disclosed related art technologies to temporarily fix the diaphragm and the piezoelectric elements, the pressure liquid chamber includes components of different materials; these are such as a nozzle plate, a liquid chamber plate, and a diaphragm, which are adhered in layers. Accordingly, the components may deform by warping along with the differences in the linear expansion coefficients for different materials, and the diaphragm and the piezoelectric elements may be adhesively fixed while the diaphragm undergoes warping deformation. Further, in some cases, each of the components may have warping deformation, and the components each having warping deformation may be adhered in layers. Japanese Patent No. 2003-276207 (hereinafter referred to as “Patent Document 2”), for example, discloses a technology to improve the precision of the components by press-processing a metallic plate of one of channel plates; however, the plates may warp after the processing.
As a result, the end parts and the central parts of the piezoelectric elements may be adhered to the diaphragm having warping deformation. This may cause the difference in pressure application while bonding the piezoelectric elements and the diaphragm, leading to heterogeneous bonding at the end parts of the piezoelectric elements and the diaphragm. Moreover, the bonding state of the pressure liquid chamber at the end parts of the piezoelectric elements may also be affected, and thus, characteristics variability may occur such as ink-ejection speeds varying at different deposited positions.